Every now an again I come across something which makes me think, 'how on Earth did I not know about this?'. I was looking for a way to quickly create a tabbed interface of content out of the fields of a content type. I was halfway down the route of implementing jQuery UI's tabbed interface, when I discovered this:
Not only does it let you build tabbed content panes (horizontal and vertical), but also accordiant, fielsets and some more! So, if you haven't already tried out this module, it's really worth a good look.
Besides the front-end interface, this module allows you to use the UI enhancements on the back-end, which can be very useful for cutting down very large content formt, or just for breaking them up into fieldsets.